Modifying a Lepai LP-2020A+ (Blue PCB Type)

[chrism]

It would be very unusual for resistors to be given the designator C anything. Seems to me you might have removed some capacitors. You really need to see a circuit diagram to know what you're doing - just pulling out components because someone on a forum says so doesn't sound like a great idea to me.

Thanks for this but I don't have any issue removing the preamp stage from the Lepai and the bypass works a treat (the mod is well documented elsewhere). I was actually asking a more specific question about doubling up on output / input decoupling benefits.

Regards

Chris

[RothwellAudio]

Sorry, I didn't intend to offend, but alarm bells ring when I hear someone say they have removed some resistors and they're actually capacitors.
BTW, I did answer your specific question.

[chrism]

Hi Andrew, You didn't although I was a bit confused by the reply.

The datasheet for the TA2020 does not go into this sort of detail.

I am looking at the signal decoupling and am aware that lots of products have output decoupling capacitor and again another capacitor on the input. I could just remove the Lepai input ones and see how it sounds but thought that I would call on others that may already have experience with this before I did.

Regards

Chris

[RothwellAudio]

You would need to know what the circuit is to be sure, but as long as the input to the power amp has no DC resistance to ground you would be ok to remove the capacitor. However, is there a resistor at the pre-amp's outputs? It wouldn't be unusual if there were, and it that case it could make a real mess of the power amp's input biasing arrangement, which might make a real mess of your loudspeakers. Or maybe not.

[chrism]

Not sure about the Lepai's power amp input being affected in this way as the Beresford DAC Pre-amp out works well with a range of different power amps.

Anyone else?

[RothwellAudio]

Depends what the circuit is. Certainly a conventional power amp with a long tail pair at the input needs to be DC blocked to prevent DC offsets at the output. Many single rail circuits need to be DC blocked at the input to prevent the circuit's bias voltage from being affected by DC paths at the input.

[Firebottle]

Andrew's right, it looks like there is a bias voltage on the TA2020 input pins, so you do need a capacitor as a dc block.

[chrism]

Thanks Alan, I will leave the 2.2uf film caps that I put in it.

Regards Chris

[chrism]

Just thought that I should post how far I have now got with the Lepai Power Amp project. 2.2uf Input decoupling caps now in place and .47uf output caps - Vishay MKT1822 caps on the output. Tidied the cabling up a bit as well.

Next job is to address the DC at the output being different on each channel - was like this before I started though (appears to be a common problem on the Lepai).

Sounds great and a far cry from the original Lepai - very clear and smooth sound and the metallic edge on highs now gone.

A picture of the mods so far.

Regards

Chris

[danilo]

I just a couple of weeks ago .. Finally.. put into my trash bin 3 Lepais that I modded.
Far more extensively than yours actually. Hey, you haven't done the Coils.. yet.
First Lepai; lived 1 week, Second one; 2 days. Third one close to a month. Wasn't willing to try a 4th one.
Typically they lose a channel, go intermittant. Inevitably going completely dead... Yippeee!
Fully addicted, a year or so into the adventure, I even built a Tripath evaluation circuit /amp from scratch.
Complete failure, as the chip, despite vendors vociferous claims, was a bad copy Fake.
As I inevitably realised, were ALL the others.
My Lepais and accumulation of 'spare' ta 2020 chips were Chinese Fakes.
Not much Sherlock required to realise that the Decade + dead Tripath firm was no longer producing chips.
Sadly Genuine Ta chips were pretty good music makers. The Fakes are decidedly not.

Try and get a hold of a 41hz.com Amp 6 gizmo ? As these featured Genuine Tripath chips.
Damned things worked really quite well TBH. Well worth owning.
Rare as hens teeth Now though.

Failing that I suggest an Lm3886 chip amp.
Say a Neurochrome or My Ref circuit.
LM 3886 chips when bought from a Genuine supplier are Good.. far better than the tripath designs,
AND still in current production.

Anyways you are clearly having fun.
Hell, I spent almost 2 years fooling about with the 2020's.
G 'luck.